Alkyl-aryl alcohol resins are useful in a variety of inks and other coatings. When used in non-aqueous ballpoint pen inks, alkyl-aryl alcohol resins provide a highly viscous ink that typically performs well over a large temperature range, typically from below 0.degree. C. to temperatures experienced in the tropics, and maintains a flow capacity that allows the immediate start of writing, while assuring smooth, continuous writing over the temperature range without skipping, running, spotting, or droplet formation at the pen tip, even under conditions of high temperature and humidity.
One prior art method commonly used to form an alkyl-aryl alcohol resin was to hydrogenate an alkyl-aryl ketone/formaldehyde resin, such as that disclosed in U.S. Pat. No. 4,731,434 to Dorffel et al.
Alkyl-aryl ketone/formaldehyde resins may be formed by mixing formaldehyde, acetophenone, and a strong base, such as KOH, in methanol at reflux. The only acidic proton in the solution, the a-hydrogen to the carbonyl, is removed by the base to form an enolate, which can attack electron-deficient sites, such as the carbonyl carbons of the formaldehyde and the acetophenone. As aldehydes are more susceptible to nucleophilic attack than ketones, the enolate preferentially attacks the carbonyl carbon of the formaldehyde, forming an alkoxide. The alkoxide extracts a hydrogen from the methanol solvent, regenerating the base, and forming 3-hydroxy-1-phenyl propan-1-one. Further extraction of .alpha.-hydrogen by the base results in the elimination of the OH group, and the formation of a vinyl phenyl ketone, which is formed preferentially because of the stability of the conjugated double bonds. By maintaining the basic conditions at a temperature of greater than 25.degree. C., the .alpha.,.beta.-unsaturated ketone polymerizes to form the desired polymeric alkyl-aryl ketone resin.
In the prior art, the polymeric alkyl-aryl ketone was typically converted to a polymeric alkyl-aryl alcohol resin by reducing the polymeric ketone resin under conditions of high pressure and temperature, typically about 300 bar at about 135.degree. C. to about 220.degree. C., in the presence of hydrogen gas, nickel, and a chromium activated copper catalyst. These conditions result in the transfer of one hydrogen to each carbonyl carbon and each carbonyl oxygen, giving the desired polymeric alkyl-aryl alcohol.
However, heavy metal catalysts are toxic, and cause handling and waste disposal problems. Moreover, the required high temperature and pressure conditions, as well as the use of hydrogen gas, are hazardous. Therefore, a need exists for a relatively low temperature and pressure process for forming polymeric alkyl-aryl alcohol resins that does not require heavy metals. The present invention provides such a process.